skip to main content

DOE PAGESDOE PAGES

Title: Mechanism of Substrate Translocation in an Alternating Access Transporter

Transporters shuttle molecules across cell membranes by alternating among distinct conformational states. Fundamental questions remain about how transporters transition between states and how such structural rearrangements regulate substrate translocation. Here, we capture the translocation process by crystallography and unguided molecular dynamics simulations, providing an atomic-level description of alternating access transport. Simulations of a SWEET-family transporter initiated from an outward-open, glucose-bound structure reported here spontaneously adopt occluded and inward-open conformations. Strikingly, these conformations match crystal structures, including our inward-open structure. Mutagenesis experiments further validate simulation predictions. Our results reveal that state transitions are driven by favorable interactions formed upon closure of extracellular and intracellular “gates” and by an unfavorable transmembrane helix configuration when both gates are closed. Finally, this mechanism leads to tight allosteric coupling between gates, preventing them from opening simultaneously. Interestingly, the substrate appears to take a “free ride” across the membrane without causing major structural rearrangements in the transporter.
Authors:
 [1] ;  [1] ;  [1] ;  [2] ;  [1] ;  [1]
  1. Stanford Univ., CA (United States).
  2. Carnegie Inst. of Science, Stanford, CA (United States)
Publication Date:
Grant/Contract Number:
FG02-04ER15542
Type:
Published Article
Journal Name:
Cell
Additional Journal Information:
Journal Volume: 169; Journal Issue: 1; Journal ID: ISSN 0092-8674
Publisher:
Elsevier
Research Org:
Carnegie Inst. of Science, Stanford, CA (United States)
Sponsoring Org:
USDOE; National Institutes of Health (NIH); National Science Foundation (NSF); Alfred P. Sloan Foundation; Harold and Leila Y. Mathers Charitable Foundation; Stanford University
Country of Publication:
United States
Language:
English
Subject:
59 BASIC BIOLOGICAL SCIENCES; molecular dynamics (MD) simulation; membrane protein; transporter; sugar transporter; SemiSWEET; structure
OSTI Identifier:
1429555
Alternate Identifier(s):
OSTI ID: 1398626; OSTI ID: 1473844

Latorraca, Naomi R., Fastman, Nathan M., Venkatakrishnan, A. J., Frommer, Wolf B., Dror, Ron O., and Feng, Liang. Mechanism of Substrate Translocation in an Alternating Access Transporter. United States: N. p., Web. doi:10.1016/j.cell.2017.03.010.
Latorraca, Naomi R., Fastman, Nathan M., Venkatakrishnan, A. J., Frommer, Wolf B., Dror, Ron O., & Feng, Liang. Mechanism of Substrate Translocation in an Alternating Access Transporter. United States. doi:10.1016/j.cell.2017.03.010.
Latorraca, Naomi R., Fastman, Nathan M., Venkatakrishnan, A. J., Frommer, Wolf B., Dror, Ron O., and Feng, Liang. 2017. "Mechanism of Substrate Translocation in an Alternating Access Transporter". United States. doi:10.1016/j.cell.2017.03.010.
@article{osti_1429555,
title = {Mechanism of Substrate Translocation in an Alternating Access Transporter},
author = {Latorraca, Naomi R. and Fastman, Nathan M. and Venkatakrishnan, A. J. and Frommer, Wolf B. and Dror, Ron O. and Feng, Liang},
abstractNote = {Transporters shuttle molecules across cell membranes by alternating among distinct conformational states. Fundamental questions remain about how transporters transition between states and how such structural rearrangements regulate substrate translocation. Here, we capture the translocation process by crystallography and unguided molecular dynamics simulations, providing an atomic-level description of alternating access transport. Simulations of a SWEET-family transporter initiated from an outward-open, glucose-bound structure reported here spontaneously adopt occluded and inward-open conformations. Strikingly, these conformations match crystal structures, including our inward-open structure. Mutagenesis experiments further validate simulation predictions. Our results reveal that state transitions are driven by favorable interactions formed upon closure of extracellular and intracellular “gates” and by an unfavorable transmembrane helix configuration when both gates are closed. Finally, this mechanism leads to tight allosteric coupling between gates, preventing them from opening simultaneously. Interestingly, the substrate appears to take a “free ride” across the membrane without causing major structural rearrangements in the transporter.},
doi = {10.1016/j.cell.2017.03.010},
journal = {Cell},
number = 1,
volume = 169,
place = {United States},
year = {2017},
month = {3}
}